Contactless smart cards are used to realize a short-range transmission of information between a reader and a chip integrated into an electronic module of the smart card without inserting the card in a reader and without any electrical connection between the reader and the metallic contacts of the electronic module.
To this end, a contactless smart card has an antenna connected to the chip for radiofrequency communication between the card and the card reader. Because a contactless smart card has neither energy source nor energy storage, such an antenna enables powering up the chip of the card be by induction.
Traditionally, such a smart card is in credit card format and the smart card antenna 3 is disposed on the substrate 4 of the card body, as illustrated on FIG. 1. The antenna is thus connected to the chip trough the electronic module 2. Such antenna has sufficient size for ensuring electrical power to the chip.
Nevertheless, constantly increasing the miniaturization of the electronics systems makes today necessary the integration of contactless chips into supports having much lower dimensions than those of a credit card. The antenna 3 connected to the chip 1 can no longer be placed into a card body and must be integrated into the electronic module 2, as illustrated on FIG. 2. The antenna is thus connected directly to two contacts La and Lb of the chip 1. The chip 1 also comprises a capacitor C used to bring the antenna into resonance. However, the small space available into such a module does not permit to include in it an antenna having the same size than those residing in existing contactless smart card bodies. The energy that an antenna integrated into an electronic module can collect will be much lower, perhaps too low to be sufficient for ensuring a correct power supply of the chip.
Therefore, there is a need for a system to ensure proper electric power supply to a contactless chip, while respecting the constraints of low available surface area imposed by the small dimensions of the electronic module in which the chip is integrated.